A US drone strike killed three suspected Al-Qaeda militants at dawn on Tuesday in the second such attack in Yemen in three days, a tribal source told AFP. \"The car in which the three were travelling -- two Yemenis and a Saudi -- was blown to pieces and all of them were killed outright,\" the source said. The attack struck in Shabwa, a southern province that borders Abyan, where Saturday night\'s strike hit. \"It was carried out by a US drone,\" the source said.